Filter devices for the filtration of fluids are known in a wide variety of embodiments. For increasing the filtering area of the filter element exposed to the flow to be filtered, known filter elements comprise a plurality of filter material layers pleated or laid in a zig-zag or serpentine line. For stabilizing this configuration of the filter material layer, the known filter elements are provided with support structures. Examples of filter elements of this type are disclosed in EP 0 256 772 A1, DE 15 07 757 A1, DE 29 06 123 A1 and DE 35 26 572 A1. Further, there are known filter elements for bag filters consisting of a plurality of pocket-shaped filter units arranged side by side, each of these filter pockets being formed of two interconnected material structures. Such filter elements are disclosed in DE 16 07 665 A1 and DE 31 32 998 C2. The filter units of these known filter elements comprise either a rigid self-supporting filter material or filter cloths, felt materials or non-wovens. In the latter case, for creating the filter unit, a support structure must be provided which keeps the filter unit open. From DE 21 28 309 A1, there is known a filter unit for gas filters having filter materials arranged between its material structures. The gas to be cleaned flows through the material structures of the filter unit while being cleaned by the interposed filter material.
Finally, DE 23 45 820 A1 discloses a further filter element with filter units wherein the material structures consist of a material suitable for the filtration of air. As has been the case in the above filter elements comprising filter units, the shape of the filter units of this filter element is established and maintained by special support structures or by the to-be-filtered flow itself or by frame constructions.
A problem in all of the above mentioned filter elements is posed by the requirement to lend mechanical stability to the filter units so as to prevent collapse of filter units while the filter elements has the fluid streaming therethrough.
It is an object of the invention to provide a filter element which, while providing an increased filtering area, has sufficient mechanical stability without requiring separate support structures.